An addition manufacturing technique is a technique for obtaining a desired three-dimensional molded product in the following manner. According to this technique, a thermoplastic resin, a photocurable resin, a powdered resin, a powdered metal, or the like is fused and cured based on three-dimensional shape data by melt extrusion, inkjet, laser light, an electron beam, or the like, and is laminated in a thin film form. A molded product is obtained directly from the shape data, and a complicated shape such as a hollow shape or a meshed shape can be integrally molded. Therefore, a field of application has been expanded to medical and aircraft industries, an industrial robot, and the like in addition to creation of a small lot or custom made test model.
In order to obtain a three-dimensional molded product, an addition manufacturing apparatus generally called a 3D printer is used. Specifically, an inkjet ultraviolet curing type using a photocurable resin such as acrylic, and a heat melting lamination type using a thermoplastic resin such as an acrylonitrile-butadiene-styrene resin are known. In addition to these types, powder molding type and optical molding type 3D printers are known.
According to the addition manufacturing technique, a three-dimensional molded product having a complicated shape can be formed. However, when a hollow structure is manufactured, a three-dimensional molded product is deformed by its own weight. In order to prevent this deformation, a shape supporting support is required. In a case of a powder molding type in which a powder raw material is bonded or fused, an unbonded or unfused powder acts as a support. After molding, the unbonded or unfused powder is scraped off, and a three-dimensional molded product can be thereby obtained. On the other hand, in an inkjet type in which a photocurable resin is gradually cured, or a heat melting lamination type in which a thermoplastic resin is melted, extruded, and laminated, it is necessary to form a three-dimensional molded product formed of a model material and a support formed of a support material almost at the same time. Therefore, it is necessary to provide a step of removing a support material from a three-dimensional molded product after molding.
However, removing a support material after molding is not easy work at all. The support material is fused, adheres, or sticks to an intended three-dimensional molded product. Therefore, in work of peeling the support material from the molded product, a means such as peeling the support material manually using a spatula, a brush, or the like, or blowing off the support material with a water jet is usually used. However, there is a risk of breakage of the three-dimensional molded product. Therefore, necessity of careful work has been a large burden.
Therefore, as the support material, a thermoplastic resin, a hot melt wax, a material which can be dissolved in water or an organic solvent, a water-swellable gel, or the like is used. A separation method utilizing heating, dissolution, a chemical reaction, power washing such as hydraulic washing, electromagnetic wave irradiation, a thermal expansion difference, or the like according to a property of a support material has been proposed (Patent Literatures 1 and 2). Specifically, use of a resin which can be easily peeled from a model material (Patent Literatures 3 and 4), melt-removing a support material by heat using a wax as the support material (Patent Literature 5), a means for dissolving or dispersing a support material in an alkali, water, or an organic solvent (Patent Literatures 6 to 11), and a means for removing a support material using an electrolyte solution such as tetramethylammonium hydroxide as a washing liquid under stirring or energizing (Patent Literature 12) have been proposed.
However, also in these support materials, it is extremely difficult to efficiently remove a portion with which details are clogged. In addition, when a method for melt-removing a wax or the like by heat is used, an oily residue adheres to a surface of a three-dimensional molded product after removal. Therefore, finishing work for the three-dimensional molded product such as wiping is required. Furthermore, a wax penetrates into the model material by heating. As a result, a surface state of the three-dimensional molded product is deteriorated disadvantageously.
On the other hand, even when a support material is removed by dissolving, dispersing, or swelling the support material in an alkaline aqueous solution, water, or an organic solvent, the support material which has been collapsed due to dissolution, dispersion, or swelling adheres to a three-dimensional molded product immersed in a washing tank. As a result, a surface of the three-dimensional molded product is contaminated. Therefore, similarly, finishing work for the three-dimensional molded product such as wiping a surface is required. In addition, it is necessary to provide a treatment step or a collecting step suitable for each of an alkaline aqueous solution, an organic solvent, and an acidic aqueous solution generated by removal of a support material containing an acidic substance after removal of the support material.
Furthermore, in an inkjet printing type using an active energy ray, molding accuracy of an interface is lowered due to a compatibilized or mixed state generated near a contact surface before curing by a support material and a model material. As a result, finishing accuracy of a three-dimensional molded product is lowered, for example, a surface of a contact portion is roughened after removal of the support material.
Under such circumstances, as a three-dimensional optical molding support material, development of a support material capable of being removed easily, requiring no finishing step after removal, and capable of acquiring a highly accurate three-dimensional molded product has been desired.